MILWAUKEE  Paul Ryan works out and watches his diet, but a new study shows that clean living can only go so far to help people like the vice-presidential candidate overcome a strong family history of heart disease.

The study of 4 million people  the largest ever on heart risks that run in families  found that having a close relative die young of cardiovascular disease doubles a persons odds of developing it by age 50. This risk was independent of other factors such as high cholesterol, high blood pressure and diabetes, and was even higher if more than one close family member had died young.

Ryan has said his father, grandfather and great-grandfather all died of heart attacks in their 50s, and the 42-year-old Wisconsin congressman has cited that as the reason for his devotion to exercise.

Id sure like to see him in my clinic, said Dr. Patrick McBride, a preventive cardiology specialist at the University of Wisconsin in Madison.

Heart attacks can result from genetic factors, an abnormal heart rhythm or a heart muscle problem  not just clogged arteries from poor health habits, said McBride, who had no role in this study but has published other work on the topic.

Whats important for anybody with that kind of story is that they sit down with their physician and get a very thorough, detailed family history and try to identify what factors may be present in the family  not just on their own think they can fix their problem, McBride said. Exercise alone wont obviate this risk.

Its not known if Ryan has had such an evaluation, although McBride noted that as a congressman, Ryan has excellent insurance and access to care. A Mitt Romney campaign spokesman said Ryan was not available for an interview about his health, and did not answer questions about whether Ryan is taking medicines for heart risk factors such as high cholesterol or high blood pressure.

In an email message, the spokesman, Brendan Buck, said Ryan has never smoked, works out five times a week, eats healthy, gets regular checkups, avoids sweets and limits alcohol consumption.

The Wisconsin congressman joked my veins run with cheese when he was named Romneys running mate, but it is clear that he takes the health of his arteries seriously.

NBC News correspondent Luke Russert recently described a January 2010 conversation when Ryan asked about Russerts father, Meet the Press moderator Tim Russert, who died of heart disease at age 58 in 2008.

Ryan urged Luke Russert to increase the cardiovascular level of his workouts and commiserated about the bad aftertaste of fish oil supplements, which some people take to try to ward off heart disease, the younger Russert wrote on an NBC blog.

Ryans family history of heart disease is dramatic, and his efforts to modify whatever risks he can control is very wise, said the leader of the new study, Dr. Mattis Ranthe, a scientist at the Danish Ministry of Health.

The study involved 4 million people from Denmark, which has detailed medical registries on families dating to 1949 because of universal health care. Researchers zeroed in on people who had developed cardiovascular disease, such as clogged arteries, heart failure, a rhythm problem or trouble with a valve, by age 50.

The chance of this was almost doubled if someone had a close relative  a parent, sibling or child  who died of cardiovascular disease before age 60. Losing two or more close relatives to cardiovascular disease by age 60 more than tripled the odds that someone would develop it before age 50.

Having a less-immediate family member, such as a grandparent, die young of cardiovascular disease also modestly increased a persons risk of early-onset heart disease  by 19 percent. As the number of early deaths in a family rose and the age at which they died fell, a persons risk of early heart disease rose up to 10-fold, researchers found.

The Danish Heart Foundation paid for the study, which was published last week in the Journal of the American College of Cardiology.

Dr. Svati Shah, medical director of Duke Universitys adult cardiovascular genetics clinic, noted that researchers saw a strong risk from family history even after taking into account traditional heart hazards such as high cholesterol and high blood pressure.

Its very important to modify those, she said, but for certain individuals, there may be a genetic predisposition independent of those risk factors.

One big weakness of the study: It had no information on smoking habits. McBride said smoking a pack a day leads to about the same risk as having two family members die early of heart disease.

Doctors and the American Heart Association offer these tips to anyone with a family history of heart disease:

Learn all you can about the circumstances around a close family members death, such as the age when they developed cardiovascular disease and any risk factors such as smoking or obesity.

Be aware of symptoms of heart disease or stroke, and see a doctor if you have any.

Make sure other family members and your doctors are aware of your family history.